It has been a miserable winter for energy customers, and after a round of price rises in the autumn many of us are bracing ourselves for the next set of bills to hit the doormat. Even before they arrive it seems safe to say that most people now consider gas and electricity firms on a par with banks and smallpox.

"I would argue that, up to a point, the industry as a whole has lost customers' permission to make a profit," Ian Peters, head of residential energy at Britain's biggest energy provider British Gas, told Guardian Money. "I think that applies to every customer and across the board."

Peters, who has been with British Gas for nine years, thinks energy companies should not be forced to automatically switch customers to the cheapest deal.

He says prompting consumers to consider their options, whether they get in touch by phone, online or mobile app, has persuaded 25% of his customers to make some kind of change to their tariff in the past 12 months. "Five years ago that would have been virtually nil," says Peters, adding that only 4% of the firm's 8.4 million customers have never moved since the energy market was opened up in 1987.

We put some of your questions to him.

• Why do you charge your poorest customers the most, by forcing them on to prepayment meters and pocketing the profits?HCollider1

"There's a myth out there that those on prepayment tariffs have been forced there by the company when only 8% of our prepayment customers are repaying debt – the other 92% have chosen to be there to control their payments," he says. "I wouldn't want your readers to think that everybody on prepayment is poor. There is some correlation, but it's not a particularly strong one."

But he adds: "Prepayment meters are more expensive than credit meters and also have all the costs of the Post Office and the PayPoint network, which is where people currently vend, so there is a higher cost to operate. In a world where Ofgem wants us to operate in a cost-reflective way, that's a consideration." However, he says in nine to 12 months there will be smart meters that can act as either prepayment or credit meters, which would reduce the cost. After that, prepayment prices may start to fall.

• I have a £180 credit but my monthly direct debit hasn't been lowered to take this into account. Why does British Gas keep its customers' money?n6robot

"If I go through the whole of 2012 for all of our customer base, on a weighted average basis, our customers owed us across the year £530m, whereas we owed them £120m. Overall we are giving more interest-free credit than the other way round. That's the big picture," says Peters.

"At an individual customer level, firstly we reassess direct debits twice a year. When you get to the end of your 12-month plan, if you are over £100 in credit and we've had a recent meter read, we will automatically refund it. If you've got to a point, for whatever reason, where your consumption was very low in the middle of the year, using our online system you could give yourself a refund."

• Is he aware that his customer service agents, when dealing with frustrated, angry and confused customers who eventually get through to one of its cavernous, soulless call centres, have a habit of hitting "wrap-up" or "next call" buttons on their phones if they encounter problems they cannot deal with? MassimoV

"I'd be very, very disappointed if people were being cut off. I've not heard that before," says Peters, who adds that the customer service centres do not have targets for how quickly they have to answer calls.

"Call centres reflect the seasonal nature of our business to a degree. February and March are usually the busiest time of the year – that is because it's when bills are at their highest so we get more calls.

"It's also true that one of the effects of our new bills is that customers call us to talk about it.

"Our call volumes have gone up so we've been slightly busier because we're doing the right thing. It goes up and down over time. More and more of our customers are self-serving anyway, using digital."

"Yes. Although, in the spirit of honesty, I don't supply my own gas because I'm not on the gas main. Electricity – all my electricals, my plumbing, even my alarm system – all come from British Gas, and I pay it myself. But I'm a mile-and-a-half from the nearest gas main, unfortunately."

• You say you make a profit of £50 for every household. Is there a big range? And what do you do when people fall behind with payments?

"The way different customers engage with us creates different profit profiles. Some of it is to do with consumption, some of it is to do with debt, some of it is to do with the payment types they are on. It's not a huge range, but we have some customers who lose us money: it's an absolute fact that every customer who gets the warm-home discount is turned into a loss-making customer," he says.

"We have got others who are more profitable than £50, but there's a big concentration around the average."

He adds: "Last year we took about one million customers on to personalised payment plans to help spread their payments ... we do payment plans, we reassess their direct debits the whole time.

"We haven't disconnected a customer for debt since February 2010 and I feel so passionately about that, any request to disconnect I have to personally sign off. We do everything we possibly can to keep our customers supplied."